Perusing Amazon Underground for apps with an "Actually Free" banner? Do it while you can.

As of May 31, Amazon will no longer accept new app and game submissions for the Underground Actually Free program. The program will be completely discontinued in 2019, Amazon's Becky Young wrote in a blog post without specifying why.

Current Fire tablet users can continue to access the Underground Actually Free store and use any previously installed Underground apps. But access to Underground Actually Free store via Amazon's Appstore on Android devices will end this summer, Young added.

Launched in 2015, the Underground Actually Free program offered 100 percent free versions of popular premium titles such as OfficeSuite Professional 8, Goat Simulator and PhotoSuite 4 as well as titles with in-app purchases like Frozen Free Fall, Star Wars Rebels: Recon Missions, Angry Birds Slingshot Stella and Looney Tunes Dash! Those who use Amazon Underground don't have to pay for premium in-app features because Amazon foots the bill.

Amazon pays developers "a certain amount on a per-minute played basis in exchange for them waiving their normal in-app fees," the company explained when it launched the Actually Free program.

Current Amazon Underground developers will continue to get paid for every minute people spend in their apps, as per Amazon's developer agreement. Developers will be able to submit and publish updates to current Amazon Underground apps until 2019. For more on the transition, check out Amazon's FAQ page.

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